1. Field of the Invention
The invention relates to radio frequency identification (RFID) technology, and in particular, to using RFID tags to monitor communication signals transmitted by RFID readers.
2. Background Art
Radio frequency identification (RFID) tags are electronic devices that may be affixed to items whose presence is to be detected and/or monitored. The presence of an RFID tag, and therefore the presence of the item to which the tag is affixed, may be checked and monitored wirelessly by devices known as “readers.” Readers typically have one or more antennas transmitting radio frequency signals to which tags respond. Because the reader “interrogates” RFID tags, and receives signals back from the tags in response to the interrogation, the reader is sometimes termed as “reader interrogator” or simply “interrogator.”
With the maturation of RFID technology, efficient communication between tags and interrogators has become a key enabler in supply chain management, especially in manufacturing, shipping, and retail industries, as well as in building security installations, healthcare facilities, libraries, airports, warehouses etc.
In is important for reader signals to be received by tags. Various attributes of a communications environment may affect the ability of tags to receive reader signals. For example, obstacles in the environment may block, reflect, or attenuate reader signals. Reflection of signals may lead to “multi-path” issues, which can further lead to “RF nulls” in the environment.
Ideally, RFID readers transmit and receive RF energy in a straight line of sight with the RFID tags. However, in real implementations, this is rarely the case. Instead, the RF energy travels along multiple paths to the tag. These “multi-paths” are the product of the RF energy bouncing, reflecting, and/or being nulled by objects in the environment, including floors, walls, people, liquids, etc. The RFID environment can sometimes have “RF nulls” (e.g., dead zones) where the RF multi-paths substantially cancel, causing loss of the reader signal in the location of the null.
Thus, what is needed are ways to improve a quality of communications between readers and tags in an RFID communications environment to improve tag read rates.